Separating Sirius's Signal From Streaming-Music Noise

When it comes to streaming, everyone is starting to hear the music. But for Sirius XM Holdings, what seems like a competitive threat may prove little more than noise.

Consumers have shifted toward streaming music, as opposed to downloading it. If that wasn't already clear from the popularity of Pandora Media and Spotify, Apple's move to pay $3 billion for Beats Electronics and news Amazon.com will soon allow Prime members to stream...